Page structure and navigation
Every page has one main heading, a skip link and a breadcrumb trail. The mobile menu uses the browser's standard disclosure control, so its links remain available without JavaScript.
Inputs, errors and results
Every input has a label that a screen reader can read, with its unit shown beside it. When a calculation is completed, screen readers announce the full result as one message. If an entry is missing or outside the allowed range, the error is announced separately. Editing a field clears the old result so it cannot be mistaken for the new values.
Keyboard use
Links, buttons, form controls and menus show a visible focus style. In the cut list optimiser, adding a part moves focus to its label. Removing a row moves focus to a remaining row or the Add button instead of losing the current position.
Motion and colour
The short pencil-line movement after a calculation is decorative. It becomes effectively instant when reduced motion is requested. Red and yellow reinforce written labels and states; colour is not the only way information is communicated.
Without JavaScript and on paper
Without JavaScript, each calculator still shows a labelled worked example, formula, explanation and blank worksheet. The page states that live editing is unavailable. Browser print produces a calculation record with the page address, formula review date, print date, inputs, result, assumptions and planning-only note.